1. Field of the Invention
The present invention relates to a magnetic tape cartridge, and more particularly to a magnetic tape cartridge that improves operation accuracy and efficiency in the process of installing a release part for unlocking a reel.
2. Description of the Related Art
As a magnetic tape cartridge used as an external recording media for data backup for computers, for example, that complying with the LTO (Linear Tape Open) standard is conventionally known. As shown in FIG. 6, this type of magnetic tape cartridge is constructed by a cartridge case divided to a lower half 1A and an upper half 1B, the cartridge case including: a single reel 10 having a magnetic tape MT wound therearound; a locking plate 11 and a pressure coil spring 4 for locking the rotation of the reel 10; a release pad 50 for unlocking the reel 10; a sliding door 6 for opening and closing a magnetic tape outlet 1C defined in the cartridge case 1 across the lower half 1A and the upper half 1B; a coil spring 7 for biasing the sliding door 6 to close the magnetic tape outlet 1C; a write protect tab 8; and a cartridge memory 9.
As shown in FIG. 7, the reel 10 has at its center a hub 12 with a cup shape opening in the side of the upper half 1B (see FIG. 6). Inside the hub 12, the release pad 50, the locking plate 11, and the pressure coil spring 4 are incorporated. The bottom surface of a bottom portion 13 of the hub 12 is externally exposed from a circular opening 1D (see FIG. 6) defined at the center of the lower half 1A. On the periphery of the bottom surface of the bottom portion 13, a face gear 14 is formed which engages with a face gear formed on a spindle of a drive unit (not shown) on which the cartridge is mounted, in order to rotate the reel 10.
Inside the face gear 14, a metal plate 15 which is attracted by a magnet provided on the spindle of the drive unit (not shown) is attached.
On the bottom portion 13, three circular openings 16 are penetratingly provided in up/down direction. These openings 16 are arranged at equal intervals in the proximity of the inner perimeter surface of the hub 12, along a circumference arranged with a predetermined radius complying with the LTO standard, and each have an aperture in the width of the face gear 14. Further, at predetermined positions inner than the openings 16, three engaging portions 17 are provided in an upwardly protruding manner.
The locking plate 11 has a plate body 11A with a cup shape that can be housed in the hub 12 of the reel 10. At a predetermined position on a bottom surface of a bottom portion 11B of the plate body 11A, a hub-side engaging portion 11C is formed which is capable of detachably engaging with the engaging portions 17 of the reel 10.
The locking plate 11 has, at the center of the top surface of the plate body 11A, four half-side engaging portions 11D provided in an upwardly protruding manner, which is in full-time engagement with a protrusion 1E with a cross shape provided at the center of the inner surface of the upper half 1B (see FIG. 6).
The locking plate 11 is downwardly biased by the pressure coil spring 4 externally attached to the half-side engaging portions 11D and provided between the locking plate 11 and the upper half 1B, and consequently the hub-side engaging portion 11C disengageably engages with the engaging portions 17.
The release pad 50 has a pad main body 50A with a disc shape from which three arm portions 50B extend in three directions at equal intervals. The arm portions 50B each have an unlocking pin 50C with a columnar shape downwardly extending from the tip thereof.
The arm portions 50B are each located between the engaging portions 17 provided on the bottom portion 13, with the unlocking pins 50C introduced through the openings 16 in the bottom portion 13.
At the center of the pad main body 50a, a spherical protrusion 11E is formed which engages with a spherical dent (not shown) provided at the center of the bottom surface of the bottom portion 11B.
Thus, in such magnetic tape cartridge, biasing force of the pressure coil spring 4 provided between the upper half 1B and the locking plate 11 causes the hub-side engaging portion 11C to engage with the engaging portions 17 protrudingly provided on the top surface of the bottom portion 13 of the hub 12 of the reel 10, thereby maintaining the reel 10 in a locked state.
Further, when the magnetic tape cartridge is mounted in the drive unit (not shown) and the hub 12 is rotated by a spindle of the unit, a face gear formed at the top of the spindle presses the unlocking pins 50C toward the upper half 1B (see FIG. 6), causing the locking plate 11 to move toward the upper half 11B against the pressure coil spring 4. This causes the hub-side engaging portion 11C to disengage from the engaging parts 17, thus unlocking the reel 10.
In the process of mounting the release pad 50 to the hub 12, of the assembling processes of the magnetic tape cartridge thus constructed, first the lower half 1A (see FIG. 6) to which those parts such as the reel 10 are attached and set on a parts conveying pallet (not shown), is conveyed by a belt conveyor. The lower half 1A comes to a stop on reaching a predetermined position near a robot (not shown).
An image processing camera (not shown) provided above the position photographs the openings 16 on the bottom portion 13 in the hub 12 of the reel 10 as shown in FIG. 8. Then, an image processor (not shown) detects the centers of the openings 16.
On the basis of the centers, the processor computes an angle α deviated, for example, in a clockwise direction from normal positions R. In order to correct the deviation of angle α, an apparatus provided below the belt conveyor (not shown) rotates the reel 10 by the angle α to align the openings 16 with the normal positions R.
Into the hub 12 on the reel 10 thus aligned, the robot holds and inserts the release pad 50 prealigned as shown in FIG. 7 and placed on the parts conveying pallet. The unlocking pins 50C are inserted into the openings 16 aligned with the normal positions R, and therewith the process of mounting the release pad 50 into the hub 12 completes. See Japanese Patent Application Laid-Open (Kokai) No. 2003-85930 (FIGS. 12–14), for example.
However, when the camera photographs the openings 16 in the process of mounting the release pad 50, the openings 16 become dark inside because the reel 10 is placed on the belt conveyor. This makes the openings 16 unclear on the photographed image, making it difficult for the image processor to precisely recognize the openings 16, which lead to a problem of decreased precision in the image processing for obtaining each center of the openings 16 and lengthened processing time.
Therefore, the present invention aims to solve the aforementioned problem, and to provide a magnetic tape cartridge capable of improving operation accuracy and efficiency in the process of mounting the release part for unlocking the reel into the hub.